The invention disclosed herein improves certain TV systems transmitting coarsely quantized samples of the combination of a conventional video signal with a suitable dithering signal (called a dither). If the stream of dither-quantized samples is transmitted over an analog channel, similar to those used for conventional analog television, the samples can be regenerated to remove significant amounts of noise and interference; and if the samples are sent in digital form over a digital channel, the number of bits per sample is reduced, with corresponding reduction in the required channel bandwidth.
An undithered luminance or chrominance component of TV loses pictorial information when the signal amplitudes are restricted to a few quantum levels; the fewer the levels, the more visibly distorted is the image. Dithering in accordance with prior art superimposes dots of stipple on the quantized picture and the latter transmit perceptible information that would otherwise be lost. Efficient dithering patterns of prior art tend to maximize the amount of information transmitted in overlaid stipple while minimizing the visibility of the dots. Preferred TV dithers include the multiphase ordered dithers of the copending application Ser. No. 07/461,009 now U.S. Pat. No. 5,148,273, especially those called self-interpolating.
Stipple dots produced on, say, the luminance component are intensity increments added to single pels. In accordance with prior art, the relation between dithering signal amplitude and the number of quantum levels insures that said increments (i.e. dot amplitudes) are fixed at one quantum step while the population density of dots varies locally on the TV raster. With multiphase dithering (sometimes called cinematic dithering), the pattern of dots changes from frame to frame, of the picture, and low-pass spatio-temporal filtering by the human psychophysical system reduces visibility of stipple dots per se relative to the pictorial information that their population distribution transmits.